Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/16—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on silicates other than clay
  • C04B35/18—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on silicates other than clay rich in aluminium oxide
  • C04B35/195—Alkaline earth aluminosilicates, e.g. cordierite or anorthite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/14—Silica and magnesia

Definitions

• the present invention relates to a method for producing a cordierite ceramic honeycomb structure by extruding.
• Cordierite ceramic honeycomb structures are used as an exhaust gas purifying catalyst carrier, a filter, or a heat exchanger for automobiles or the industrial use.
• a production method of a cordierite ceramic substrate disclosed in Japanese Patent Application Laid-Open No. 51-5313 mentions that the firing process can be conducted economically without generating a crack while maintaining characteristics necessary for a honeycomb substrate by reducing the amount of unprocessed clay (raw clay) included in the clay component in the material batch and replacing the same by processed clay (calcined clay) in preparing clay, talc and alumina materials for producing a honeycomb substrate having a cordierite phase as the main component.
• Japanese Patent Application Laid-Open No. 56-145171 discloses a technology for producing a cordierite body having the excellent thermal impact resistance, capable of conducting the firing process at a comparatively low temperature by using halloysite as the kaolin mineral and plate-like talc particles as the talc.
• a thinner wall and a higher cell density are desired particularly for a honeycomb carrier of a ceramic honeycomb catalyst carrier to be used for an exhaust gas apparatus for automobiles in order to improve the purifying performance according to the progress of the industrial technology.
• a cordierite ceramic honeycomb structure is produced by extruding in order to improve the mass productivity.
• the method of replacing the raw clay by the calcined clay disclosed in Japanese Patent Application Laid-Open No. 51-5313 remarkably deteriorates the formability at the time of extruding although the method is effective for reducing crack generation at the time of firing.
• the method using halloysite disclosed in Japanese Patent Application Laid-Open No. 56-145171 can improve only the thermal impact resistance but the improvement in the formability in production cannot be expected.
• an object of the present invention is to provide a production method of a cordierite ceramic honeycomb structure, capable of coping with a honeycomb structure with a thin partition wall by improving the formability (in particular, the lubricity and the shape stability) and preventing generation of a crack in the firing process, and thus suitable for the mass production in extruding.
• a production method of a cordierite ceramic honeycomb structure having cordierite as the main component of the crystalline phase which comprises: adding a forming auxiliary agent to a cordierite material to obtain a mixture, kneading the mixture to obtain a material batch, forming the material batch by extrusion to form a honeycomb structure, drying the honeycomb structure to obtain a dried body, and firing the dried body, wherein clay mineral, which is one component in the cordierite material batch for extruding, contains dickite and at least one selected from the group consisting of kaolinite and halloysite, with a 5 to 50% by weight dickite amount in the clay mineral.
• the average particle size of the dickite in the clay mineral is 10 ⁇ m or less, and extrusion dies with a 110 ⁇ m or less slit width are used.
• the coefficient of thermal expansion between 40 to 800°C of the cordierite ceramic honeycomb structure in the direction to the flow passages is 0.8 x 10 -6 /°C or less.
• clay mineral which is one component in the cordierite material batch for extruding, contains dickite and at least one selected from the group consisting of kaolinite and halloysite, with a 5 to 50% by weight dickite amount in the clay mineral.
• the formability in particular, the lubricity and the shape stability
• the formability which has not been realized with kaolinite, halloysite or a combinaiton thereof, can be improved as well as crack generation can be prevented in the firing process
• the amount of the dickite in the clay mineral is 5 to 50% by weight in a production method of a cordierite ceramic honeycomb structure of the present invention.
• the reason thereof is that the chance of crack (firing tear) generation in the firing process is increased and the formability is deteriorated with a less than 5% by weight dickite amount in the clay mineral.
• the clay mineral (unprocessed clay) used consists only of dickite and at least one of kaolinite and halloysite.
• the average particle size of dickite in the clay mineral is preferably 10 pm or less, more preferably 7 ⁇ m or less in order to improve the poor sintering reaction of the dickite in the firing process.
• the coefficient of thermal expansion between 40 to 800°C of the cordierite ceramic honeycomb structure obtained in the present invention in the direction to the flow passages is 0.8 ⁇ 10 -6 /°C or less.
• the coefficient of thermal expansion (between 40 to 800°C) in the vertical direction to the flow passages is preferably 1.0 ⁇ 10 -5 /°C or less for the reason the same as the above-mentioned.
• the particle size was measured with Sedigraph (X-ray sedimentation method) produced by Micromeritech Corp.
• the chemical analysis value was measured by the fluorescent X-ray spectroscopy.
• honeycomb structure honeycomb sintered body
• honeycomb sitered body With a honeycomb structure (honeycomb sitered body) inserted in a flexible tube, the pressure (kg/cm 2 ) at which partial breakage was generated by applying a uniform hydraulic pressure was measured (average value of 10 specimens).
• cordierite material unbaked clay for extruding was prepared such that a cordierite composition can be provided after firing each batch, using talc, unprocessed clays (kaolinite, dickite, and halloysite), calcined clay, alumina, aluminum hydroxide, and silica with chemical analysis values shown in Table 1, with the ratio of the unprocessed clay changed as shown in Table 2, by adding methyl cellulose and an organic forming auxiliary agent, and kneading.
• unprocessed clays kaolinite, dickite, and halloysite
• calcined clay alumina, aluminum hydroxide
• silica silica
• a cylindrical honeycomb structure (honeycomb compact) with a 100 mm diameter and a 150 mm height, having a square cell shape with a 76 ⁇ m rib thickness and a 62 pieces/cm 2 cell number was formed by a known extruding method.
• the formability thereof was evaluated by the lubricity (extrusion pressure for obtaining a constant forming speed) and the shape stability (stress for crushing a honeycomb structure from the above immediately after extrusion).
• honeycomb sintered body honeycomb structure
• honeycomb structure was produced by drying the honeycomb compact (honeycomb structure) and firing with a 1420°C firing maximum temperature for 35 hours (economical firing time), and the ratio of the firing tear (crack), the coefficient of thermal expansion [CTE] (the direction to the flow passages of the honeycomb sintered body), the thermal shock resistance [Esp], and the isostatic strength [ISO] were measured. Results are shown in Table 2.
• the dickite amount was appropriate (the dickite amount in the clay mineral was 5 to 50% by weight) in Examples 1 to 10, the ratio of generating firing tear was 0% as well as the formability and the honeycomb characteristics were also good.
• the coefficient of thermal expansion [CTE] (the direction to the flow passages of the honeycomb sintered body) was 0.8 ⁇ 10 -6 /°C or less, the thermal shock resistance [Esp] becomes 700°C or more so that it can be used as an exhaust gas catalyst carrier for automobiles.
• cordierite material unbaked clay for extrusion molding was prepared such that a cordierite composition can be provided after firing each batch, with chemical analysis values, talc, unprocessed clays (kaolinite and dickite), calcined clay, alumina, aluminum hydroxide, and silica shown in Table 3, with the ratio of the unprocessed clay changed as shown in Table 4, by adding methyl cellulose and an organic forming auxiliary agent, and kneading.
• unprocessed clays kaolinite and dickite
• calcined clay alumina
• aluminum hydroxide aluminum hydroxide
• silica silica
• a cylindrical honeycomb structure (honeycomb compact) with a 100 mm diameter and a 150 mm height, having a square cell shape with a 76 ⁇ m rib thickness and a 62 pieces/cm 2 cell number was formed by a known extruding method.
• the formability thereof was evaluated by the flowability (extrusion pressure for obtaining a constant forming speed) and the shape stability (stress for crushing a honeycomb structure from the above immediately after extrusion).
• honeycomb sintered body honeycomb structure
• honeycomb structure was produced by drying the honeycomb compact (honeycomb structure) and firing with a 1420°C firing maximum temperature for 35 hours (economical firing time), and the ratio of the firing tear (crack), the coefficient of thermal expansion [CTE] (the direction to the flow passages of the honeycomb sintered body), the thermal shock resistance [Esp], and the isostatic strength [ISO] were measured. Results are shown in Table 4.
• the coefficient of thermal expansion [CTE] (the direction to the flow passages of the honeycomb sintered body) was 0.8 ⁇ 10 -6 /°C or less, the thermal shock resistance [Esp] becomes 700°C or more so that it can be used as an exhaust gas catalyst carrier for automobiles.
• a honeycomb structure having a thin partition wall, and suitable for the mass production can be obtained since the formability (in particular, the lubricity and the shape stability) can be improved in extruding and crack generation can be prevented in the firing process.
• the invention also extends to a cordierite ceramic honeycomb structure produced by the method of the invention.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Structural Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Catalysts (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Press-Shaping Or Shaping Using Conveyers (AREA)

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• 1997
  • 1997-08-19 JP JP22235597A patent/JP3311650B2/ja not_active Expired - Lifetime
• 1998
  • 1998-08-11 US US09/132,519 patent/US5916511A/en not_active Expired - Lifetime
  • 1998-08-18 EP EP98306593A patent/EP0897900B1/de not_active Expired - Lifetime
  • 1998-08-18 DE DE69800379T patent/DE69800379T2/de not_active Expired - Lifetime

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